Field
Aspects of the present invention generally relate to a power transmission device, a power transmission method, and a storage medium.
Description of the Related Art
Conventionally, a technique for supplying electric power in a contactless manner (by radio) has been known. As exemplary contactless power supply methods, the following four types are available: an electromagnetic induction type; a magnetic field resonance type; an electric field coupling type; and a radio wave reception type. Among these, the magnetic field resonance type is characterized in that sufficient electric power can be transmitted for a long distance, and therefore, the magnetic field resonance type has particularly attracted attention among the four types. Regarding the magnetic field resonance type, the one-to-N power supply method where a power transmission device performs power transmission to a plurality of reception devices by radio has been proposed, in which this characteristic of the long power transmission distance is taken advantage of (see, for example, Japanese Patent Application Laid-Open No. 2009-136132).
According to the technique discussed in Japanese Patent Application Laid-Open No. 2009-136132, a power transmission device performs search, by emitting a constant pulse signal in a stand-by mode when not performing power transmission, so as to determine whether any power reception device is present in the vicinities within several meters. Then, when a reception device sends its own unique ID to the power transmission device, the power transmission device determines whether a transmission source of the unique ID is a power reception device that is a power supply object. In a case where the transmission source is a power reception device that is a power supply object, the power transmission device supplies electric power to the power reception device. Here, the power transmission device can send a unique code to the power reception device, in order to receive information about the amount of charge, a state of the device, etc., individually.
The power transmission device performs power transmission at a transmission frequency at which the power reception device as a power transmission object can receive power. Here, however, any device that can receive power at a frequency that coincides with the transmission frequency can receive power, even if it is a device other than those that the power transmission device assumes as the power reception devices. This results in a problem that a third party may steal electric power.